1. Field of the Invention
The present invention pertains to a coiled tubing conveyed, hydraulically inflatable straddle packer system for use in wells. Inflation and deflation of the packers, together with control of certain valves interposed in the tubing string is carried out by solenoid actuated valves controlled from the surface.
2. Background
In certain wellbore operations, such as stimulation of a particular formation zone of interest, production of reservoir fluids and pressure testing operations, it is desired to isolate a certain portion of the wellbore by the use of two separate inflatable packers which are interconnected by a tubing string or the like, sometimes referred to as a straddle packer arrangement. In this way, a certain zone in the formation can be isolated from the remainder of the wellbore and fluids can be injected into the isolated zone or produced from the isolated zone through a tubing string connected to the straddle packer arrangement.
The conveniences of using coilable metal tubing for conveying straddle packer arrangements into and out of wellbores have made this type of system more useful. However, conventional tubing conveyed straddle packer arrangements typically rely on mechanical movement of the tubing string to effect operation of certain setting mechanisms for inflating and deflating the packers. Certain control valves in the tubing string are opened and closed by the application of hydraulic fluid pressure through the tubing string. Mechanical-hydraulic controlled straddle packer systems are difficult to operate. Packer inflation failures and other system failures are not uncommon and often result in fishing operations. Packer location in the wellbore is also usually determined solely by measuring the amount of tubing paid out as the system is lowered into the wellbore. This arrangement lacks the degree of accuracy often required for operations in short, isolated zones. Moreover, the friction and drag forces acting on the tubing string in deviated and generally horizontally extending wellbores renders mechanical movement of the tubing string for actuation purposes difficult, if not impossible, to achieve.
Accordingly, there has developed a need for a more reliable and less complex system for isolating a zone in a formation intersected by a wellbore, particularly deviated and generally horizontal wellbores, wherein more accurate depth control of the location of a straddle packer system may be accomplished and a system capable of reliable operation may be provided for use. One solution to the problems associated with prior art straddle packer systems is provided by the present invention.